Dozens of Republican senators on Tuesday called on the White House to approve the Keystone XL pipeline as foes vowed to risk arrest at protests against the controversial project.

President Barack Obama will have the final say on whether to allow the pipeline that could deliver as much as 830,000 barrels per day of Canadian oil sands crude to U.S. Gulf Coast refiners, a decision not expected for many months.

Lawmakers who favor the plan are pushing the White House to approve the project without further delay.

Keystone’s backers argue that blocking pipelines will discourage development of a region where oil is abundant, but is carbon-intensive to produce.

But opponents argue that advanced drilling methods will inevitably put vast reserves of oil sands crude within easy reach, no matter whether the Keystone project is approved or not.

“There is no question that Canada will develop these resources,” reads the letter signed by all 45 Republican senators, echoing a State Department finding from late January.

“Rejecting the Keystone pipeline will cost thousands of American jobs and prevent our country from accessing a large supply of North American energy,” said the letter authored by North Dakota Republican John Hoeven.

The State Department concluded that the $5.4 billion, TransCanada Corp pipeline will not unduly worsen climate change. But eight different U.S. federal agencies will have a chance to weigh in on the pipeline over the next three months.

Environmentalist foes of the project have challenged the State Department findings that the pipeline would not spur oil sands development or weigh on global warming.

The next several months should see a publicity blitz from opponents and backers of the pipeline to shape public opinion ahead of any decision, said Tiernan Sittenfeld, the chief lobbyist for the League of Conservation Voters.

“For an issue like climate change that can feel abstract to some people, the Keystone XL pipeline is something tangible,” she said.

On Tuesday, the League published a guide to lawmakers’ votes on environmental legislation as well as other conservation matters.

Establishment environmental groups will continue to push the Keystone issue in Washington, but other activists will make their arguments on the street, according to Danielle Droitsch of the Natural Resources Defense Council.

“We’ve been surprised by the number of spontaneous protests that popped up after the State Department report,” she said, describing about 280 “vigils” against the pipeline that were organized in recent days.

Early next month, college students from across the country are planning a march on the White House in a protest to discourage Obama on the pipeline decision.

More than 75,000 Keystone foes have promised to face arrest if called upon to protest the pipeline, according to activist group CREDO Action.

“Senator Hoeven can send a letter to the White House every day, but that is not going to be what sways this decision,” said Sittenfeld.